Acquisition of correct vowel production: a quantitative case study.

There have been relatively few studies of the course of acquisition of correct vowel production. The present study suggests this gives an illusory impression that vowels are acquired easily and are of little theoretical interest. Despite a relatively precocious rate of vocabulary acquisition over the period from 14 to 20 months, the subject studied produced less than 60% of her vowels correctly according to evidence from phonetic transcriptions. A complex pattern of vowel preferences and errors was only partially related to typical prespeech babbling preferences, but was strongly related to word structure variables (monosyllabic vs. disyllabic) including stress patterns of disyllabic words, as reflected in patterns of relative frequencies of vowels in stressed and unstressed syllables. Consonant-vowel interdependence was observed, in both the favoring of high front vowels in the environment of alveolar consonants, and a reciprocal relation between vowel reduplication and consonant reduplication in disyllabic words.